Why Can’t You Reach the Speed of Light?

A friend from high school had a good question that I wanted to share:
I have a science question!!! Why can’t we travel the speed of light? We know what it is, and that its constant. We’ve even seen footage of it moving along a path (it was a video clip I saw somewhere [Edit to add: there are now two different experiments that have done this. One that requires multiple repeats of the light pulse and a newer technique that can work with just one). So, what is keeping us from moving at that speed? Is it simply an issue of materials not being able to withstand those speeds, or is it that we can’t even propel ourselves or any object fast enough to reach those speeds? And if its the latter, is it an issue of available space/distance required is unattainable, or is it an issue of the payload needed to propel us is simply too high to calculate/unfeasable (is that even a word?) for the project? Does my question even make sense? I got a strange look when I asked someone else…
 This question makes a lot of sense actually, because when we talk about space travel, people often use light-years to discuss vast distances involved and point out how slow our own methods are in comparison. But it actually turns out the road block is fundamental, not just practical. We can’t reach the speed of light, at least in our current understanding of physics, because relativity says this is impossible.

To put it simply, anything with mass can’t reach the speed of light. This is because E=mc2 works in both directions. This equation means that the energy of something is its mass times the speed of light squared. In chemistry (or a more advanced physics class), you may have talked about the mass defect of some radioactive compounds. The mass defect is the difference in mass before and after certain nuclear reactions, which was actually converted into energy. (This energy is what is exploited in nuclear power and nuclear weapons. Multiplying by the speed of light square means even a little mass equals a lot of energy. The Little Boy bomb dropped on Hiroshima had 140 pounds of uranium, and no more than two pounds of that are believed to have undergone fission to produce the nearly 16 kiloton blast.)

But it also turns out that as something with mass goes faster, its kinetic energy also turns into extra mass. This “relativistic mass” greatly increases as you approach the speed of light. So the faster something gets, the heavier it becomes and the more energy you need to accelerate it. It’s worth pointing out that the accelerating object hasn’t actually gained material – if your spaceship was initially say 20 moles of unobtanium, it is still 20 moles of material even at 99% the speed of light. Instead, the increase in “mass” is due to the geometry of spacetime as the object moves through it. In fact, this is why some physicists don’t like using the term “relativistic mass” and would prefer to focus on the relativistic descriptions of energy and momentum. What’s also really interesting is that the math underlying this in special relativity also implies that anything that doesn’t have mass HAS to travel at the speed of light.

A graph with X-axis showing speed relative to light and Y-axis showing energy. A line representing the kinetic energy the object expoentially increases it approach light speed.

The kinetic energy of a 1 kg object at various fractions of the speed of light. For reference, 10^18 J is about a tenth of United States’ annual electrical energy consumption.

The graph above represents  the (relativistically corrected) kinetic energy of an 1 kilogram (2.2 pound) object at different speeds. You can basically think of it as representing how much energy you need to impart into the object to reach that speed. In the graph, I started at one ten thousandth the speed of light, which is about twice the speed the New Horizons probe was launched at. I ended it at 99.99% of the speed of light. Just to get to 99.999% of the speed of light would have brought the maximum up another order of magnitude.

Where are all the engineering blogs?

I was browsing through Dynamic Ecology recently on my reader to catch up on end-of-2015 posts and was intrigued by one of the author’s comments on why there isn’t really an ecology blogosphere. And though I’ve pondered it before, this makes me wonder where the engineering blogosphere is. I don’t have much evidence to back up the loading of that question, but I’ve been in grad school for engineering for 3.5 years now, and it’s worth noting that I still haven’t heard of any major engineering blogs people follow. And the sheer randomness of Blogmetric’s ranking of engineering blogs seems to corroborate this: only the top 2 of the ranked engineering blogs are tracked to have over 100 visitors a month. A Github list of engineering blogs (which is currently the first result for Googling “engineering blogs”) seems incredibly focused on tech company blogs and IT/programming/development.

Engineering.com’s blog seems to have ended without even a goodbye at the end of 2014. Engineer Blogs has been radio silent since September of 2012. And the American Chemical Society’s magazine, Chemical & Engineering News, closed up nearly all of its blogs in mid-2014, with an explanation implying this was because they were viewed as a drain on resources that could be more productively used for other tasks. Chemical Engineering World (which as far as I can tell, is a personal blog and not affiliated to the Indian publication of the same name) seems to have just came back after a hiatus.

The Dynamic Ecology post’s second point on ecology not being very news-driven sounds compelling to me as a reason that could easily cross-apply to engineering, especially if you’re trying to move away from just tech company gossip. Having something well-known to react to can make it easier to post content that’ll actually engage readers because they start searching for it. Point 1 of the Neuroecology post’s on neuroscience lacking a blogosphere because neuroscience bloggers focus more on outreach to general audiences than technical exchanges with each other also seems valid. What’s interesting is the comparison I’m making. As Jeremy from Dynamic Ecology points out, the general science blogosphere is pretty vibrant. He and the Neuroecologist are focusing more on the lack of interacting blogging communities in specific disciplines. Engineering seems to lack this at both levels. I also wonder about some specific issues in engineering that can contribute to this.

  • Is engineering too broad to have a meaningful blogosphere? I see two distinct forces here.
    • First, is the breadth of engineering disciplines. I could see it being hard for there to be a lot of substantive discussion between, say, a chemical engineer and a computer scientist on a broad range of topics.
    • Second, there’s the huge influence of a lot of engineering actually being done in industry. I’m not going to say academic and corporate engineers don’t talk to each other, but it would also be dumb to pretend they have the same interests in how they approach outreach.
  • Is engineering too tied into the science blogosphere? (I wondered a similar thing last time I posted about engineers and outreach) Interested scientists and science writers can (and do) do a good job of explaining concepts and results from related engineering fields. For instance, Dot Physics is written by a physicist who routinely covers topics that are related to technology and engineering. On the opposite end, I clearly try to cover science topics that I think I can explain, even if I’m not experts in them. Randall Munroe straddles the border a lot in What If? and Thing Explainer.
  • You might think I’m treading around one obvious potential component of an engineering blogosphere, and that’s tech blogs. But engineering isn’t just “tech companies”, which in modern parlance seems to really just mean computer and Internet companies. (I’ve somewhat ranted about this before in the last two paragraphs of this post.) A lot of stuff also goes on in physical infrastructure that engineers could talk about. And in an era where the Internet seems increasingly interested in discussion of how system shapes our lives, it seems like we’re missing out if the people who help shape physical systems don’t share their voices.

Edit to add: I also realize I didn’t include any discussion about Twitter here, mainly because I’m still a novice there. But I still haven’t seen very long discussions on specific engineering issues on Twitter, though I assume tech is the exception again.

Quick Thoughts on Diversity in Physics

Earlier this month, during oral arguments for Fisher v. University of Texas, Chief Justice John Roberts asked what perspective an African-American student would offer in physics classrooms. The group Equity and Inclusion in Physics and Astronomy has written an open letter about why this line of questioning may miss the point about diversity in the classroom. But it also seems worth pointing out why culture does matter in physics (and science more broadly).

So nature is nature and people can develop theoretical understanding of it anywhere and it should be similar (I think. This is actually glossing over what I imagine is a deep philosophy of science question.) But nature is also incredibly vast. People approach studies of nature in ways that can reflect their culture. Someone may choose to study a phenomenon because it is one they see often in their lives. Or they may develop an analogy between theory and some aspect of culture that helps them better understand a concept. You can’t wax philosphical about Kekule thinking of ouroboros when he was studying the structure of benzene without admitting that culture has some influence on how people approach science. There are literally entire books and articles about Einstein and Poincare being influenced by sociotechnical issues of late 19th/early 20th century Europe as they developed concepts that would lead to Einstein’s theories of relativity. A physics community that is a monoculture then misses out on other influences and perspectives. So yes, physics should be diverse, and more importantly, physics should be welcoming to all kinds of people.

It’s also worth pointing out this becomes immensely important in engineering and technology, where the problems people choose to study are often immensely influenced by their life experiences. For instance, I have heard people say that India does a great deal of research on speech recognition as a user interface because India still has a large population that cannot read or write, and even then, they may not all use the same language.

2015 in review

Thank you everyone for reading my blog this year! May you all have a Happy New Year!

The WordPress.com stats helper monkeys prepared a 2015 annual report for this blog.

Here’s an excerpt:

A San Francisco cable car holds 60 people. This blog was viewed about 2,100 times in 2015. If it were a cable car, it would take about 35 trips to carry that many people.

Click here to see the complete report.

A non-biologist’s guide to not saying dumb things about biology

I’m not a biologist, but even I still can see when some people make strange claims about biology. But maybe not being an expert can help here because I don’t know enough to give a super detailed explanation.

  • Nature vs nurture is really complicated. I think to some people nurture has become almost synonymous to “choice”  because of the use of this phrase in discussions about child-rearing and personal development, like the debate over whether or not people are “born gay”. But nurture also encompasses stuff in the environment that no one may reasonably have control of, like exposure to certain hormones in the womb.

dna

  • This also ties into genetic causes being hard to figure out. Many traits that are associated with a known gene aren’t completely controlled by it – it just may increase or decrease the odds of a person having it, because there are still environmental influences. The other issue is that many traits are influenced by multiple genes. For instance, 33 different parts of the human genome may be related to Alzheimer’s disease.
  • Being allergic to something doesn’t mean you are allergic to every molecule in it. This seems to come up a lot in debates on GMOs, when people raise concerns about people having allergies to novel genes. Those concerns are mostly legitimate, but it’s worth pointing out almost any new molecule we encounter could end up being an allergen. (Latex and nickel allergies  were probably surprising when they first started showing up in populations.) We could actually test if whatever a new gene expressed could cause an allergic reaction. For instance, this paper says most shellfish allergies seem to be in response to one protein. Or your may know people who are allergic to cow’s milk, but can still eat beef. And it makes sense, because a major piece of evidence supporting evolution is how similar many proteins are across different species – we share a lot proteins with all the other multicellular species on Earth.
  • One study doesn’t really prove anything. This applies to all science, but it seems to come up a lot in reactions to reporting about biology and medical studies. One study saying something about a specific effect of eating chocolate or finding a gene correlating to a disease doesn’t mean much. A hallmark of modern science is reproducibility, and so we should generally look at multiple studies before accepting things as “fact”.
  • Genetic engineering does not work like LEGOThe TV tropes link explains a lot. And the Analysis page on TV Tropes also explains how this actually works in relatively accessible detail. You won’t get wings by adding bird genes to your genome – even if you got the right Hox genes, you would also need to still ensure the right signals were sent to activate the genes to begin the appropriate limb formation.
  • Rates of change matter. When people are concerned over climate change or pollution or other impacts humans have on the environment, it’s not that ecosystems can’t adapt to any change. The issue is that if the environment changes too fast, it can outpace the speed at which organisms can adapt and cause a large number of extinctions.

Listen to The Message Podcast on Your Long Trips This Weekend

If you are one of the 46.9 million Americans travelling more than 50 miles this weekend, I have an entertainment recommendation for you. Consider listening to a new (and recently finished) science fiction podcast, The Message. Sorry if you were hoping for the pseudo “Is this actually like Serial?” illusion, but I just don’t care about every edgy series trying to make itself seem better by hiding whether or not it is actually fiction. I’d add that marathoning the series is the best way to go. There’s only eight episodes, and aside from the last one, they’re all about 13 minutes (with a minute of intro each show) so it’s a good way to spend 2 hours while travelling. I will add, that if I attempted to listen to this one week at a time, I probably would have quickly lost interest because there just wasn’t much material in each episode to feel hooked. But listening to it for two hours straight, it actually felt like a decently paced radio play and the characters and plot were all compelling enough to make up for some clunky structure. Seriously, I skipped eating lunch or getting gas on the road for an hour because I was halfway through and didn’t want to interrupt it.

Also, against the Wired piece’s concern, it didn’t seem like a super transparent plug for GE products. Unless some of the scientists they mentioned were affiliated to GE in some way, and even then, I wouldn’t find that obnoxious. The science didn’t always make sense, but it didn’t seem like technobabble. Also, I was pleasantly surprised by what seemed to be the diversity of the science team in the universe of the story – there was even a person (Mod, though I’ve also seen the spelling Maud) who went by non-binary pronouns, and the program’s director made it clear that disrespecting them wouldn’t be tolerated. I would love to talk about it more if other people have listened to it.

 

What is the point of thesis/dissertation committees?

I ask this in all sincerity, because after talking to other students in other schools and other fields, I don’t seem any closer to an answer. Maybe it’s just because I think my department is weird, because we don’t assemble dissertation committees until we propose, and we propose fairly late (it’s pretty common for people to propose only a year before they plan on defending).

The closest thing to a consensus answer I can find is that committees exist to make sure advisors aren’t just handing out degrees. But if that is the case, it seems like there isn’t really a guarantee the average committee that doesn’t do much more than read the proposal and the dissertation would be effective at that. A group of less than half a dozen people who typically have two weeks to read a ~200 page summary of what is usually years of research can’t really independently verify the results that are presented. And if a professor really was intent on just handing out degrees to their lab, they could help make that data look more convincing. (I’m not saying this happens a lot. I don’t know for sure, but I don’t think so. My point is just that it seems easy to work around the supposed purpose of committees.)

I thought the point of a dissertation committee was to be a real committee, which in my mind means that at least part of it’s power comes from the fact that it is a group. Advisors can be great and all, but sometimes you need the perspective of other people to plan an experiment or help think through an interpretation of results. I thought the committee could help mediate part of the intellectual relationship between the advisor and student. Say a student wants to redo or alter some experiment but the advisor doesn’t think that it is worth the time; the student can try to convince the committee as a group of intellectual peers, and if they agree, they can essentially override the advisor’s wishes on behalf of the student. I think this is key because it can help diffuse some negative feelings in conflicts like this away from the student. (I don’t think the committee should take on issues that rise to the point of breaking up the advising relationship. Though if this works, I also think fewer issues should lead to the break up of the relationship.) I’m not sure if the converse matters as much because advisors do generally have a lot of control over what their students do, but if an advisor felt the student wasn’t doing something well, he or she could have the committee make it clearer.

So I’ll close with two questions I would love to hear answers from people in other graduate programs. First, when does you first assemble your committee? Second, what does your committee do?