John Oliver interviews Stephen Hawking

Posted on by June 21, 2014
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This is really worth a look. British comedian John Oliver interviews Britain’s most famous scientist, physicist Stephen Hawking:


Link: http://youtu.be/T8y5EXFMD4s

Imaginary time, by the way, is a theoretical additional time dimension that eliminates singular points in theoretical analysis of spacetime, converting them into ordinary points rather than those in which the equations of physics have no solution. And no, I don’t understand that.

(Incidentally, Oliver actually gets one thing slightly wrong, saying “T equals i time t” when he should say than “tau equals i times t.” I may not understand this stuff, but at least I can tell a tau from a t when I read something in Wikipedia…)



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Faster than the speed of light is relatively fast, part deux

Posted on by July 7, 2014
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(Turns out I had used that title on a previous blog post here, but I want to use it again, and what are you going to do about it?)

I’ve been pondering lately about cosmology, which I know just barely enough about to confuse myself, and by a nifty manifestation of what a friend of mine calls the “Tab Hunter Effect,” I just saw a video from the fine folks at Veritasium that talks about the very thing I was pondering:

And just last night I ran across a scientific paper on the very same topic. The details are over my head, but at least the conclusions are in reasonably plain English.

Now here’s something that’s simple enough I worked it out by myself:

Suppose you’re in a car driving 60 miles per hour and you’re now 60 miles from where you started. How long have you been driving? Well, duh, 60 miles at 60 miles an hour; you’ve been driving an hour, right? And if you’re 300 miles from where you started and you’ve been driving 60 miles an hour, you’ve been driving five hours. Or if you’ve gone 300 miles at 30 miles an hour, you’ve been driving 10 hours. And so on. In general, elapsed time equals distance divided by speed. Again, duh.

Now imagine there’s an explosion in space sending fragments zipping outward in all directions and speeds, and with nothing to slow them down, each bit keeps zipping along at the same speed it had to start with.

The same relationship between time, distance, and speed holds true for those flying particles as for a car driving on a highway. If a particular piece of shrapnel has traveled 100 miles at 50 miles an hour, for example, the explosion must have happened two hours ago.

This is too easy. How do we make it sound more impressive? Well, let’s measure speed in kilometers per second and distance in megaparsecs (an astronomical unit equal to a little under 3.3 million lightyears). And let’s talk about speed divided by distance rather than distance divided by speed, so the result isn’t the elapsed time but 1 divided by the elapsed time. And finally, despite the fact that the value pretty obviously changes with time, let’s call it a “constant” just to mess with people.

Now, back in the 1920s an astronomer named Edwin Hubble — the guy the Hubble Space Telescope is named after — observed that galaxies (previously thought to be clouds of gas in our own galaxy) appeared to be moving away from us, and the more distant a galaxy was, the faster it was moving, and the ratio of speed to distance seemed to be pretty consistent, though Hubble’s initial estimates have since been adjusted to a much smaller number.

Today it’s estimated that a galaxy a million parsecs away is receding from us at about 70 kilometers per second. (That is, the “Hubble constant” is currently estimated as about 70 km/s/Mpc.) A galaxy that’s two megaparsecs away is receding at 140 km/s, and so on. Since the universe is expanding everywhere, we can take any point (such as this blog) to be the center of the expansion.

If the Big Bang explosion was as simple as the simple-minded explosion of my example, then the Hubble constant should work out to be 1 divided by the age of the universe. So let’s work it out and see what we get.

Type the words 1 megaparsec in kilometers into Google and it will tell you that a megaparsec is 3.08567758 × 1019 kilometers. Dividing that by 70 should give you the age of the universe in seconds. You can work that out in Google as well: Just type 3.09 * 10^19 / 70 into a Google search and you’ll get 4.4142857e+17, which happens to mean 4.4142857 × 1017), where 1017 means 10 followed by 17 zeroes. Now type 4.4142857e17 seconds in years, and you’ll get 1.39883e10 years, or about 14 billion years, which happens to be very close to the estimated age of the universe (roughly 13.8 billions years). Close enough for Star Fleet work anyway.

In fact, it seems too good to be true. The matter in the universe is attracting the other matter in the universe, which should be slowing the expansion down, and it also appears that for the last however many billion years, dark energy (which is a mystery) has been speeding the expansion up. Maybe they just cancel each other out enough for 1 over the Hubble constant to give us the age of the universe despite the naive simplicity of the calculation.

(Or maybe it has to do with this: If you compute the circumference of the cosmic microwave background based on our estimates for the expected size of its slight irregularities and divide that by our best estimate of the radius, you get a quotient of 2 pi. That may not seems so surprising, since it’s exactly what you’d expect in Euclidean space. But one of the few things I think I know about general relativity is that gravity curves space into something not Euclidean (most noticeably close to a black hole). If space is overall Euclidean, that might imply that there’s not much net gravitational influence on a cosmic scale. Perhaps helps explain why the calculation works. I don’t know.)

Well, enough of that. I’m not sure whether anybody else finds my amateur stabs at amateur cosmology interesting, but hey, it’s my blog.



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Getting home from the space station

Posted on by December 11, 2014
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Currently the only means of travel between the Earth and the International Space Station is via of a Russian Soyuz spacecraft. This fascinating European Space Agency video describes the process of returning home, and I was amazed by how scary the process sounds. For example, the so-called “soft landing” involves firing retrorockets just 70 centimeters (about 28 inches) above the ground. At least the seats are cushioned with shock absorbers. Remind me not to volunteer for this.

Link to Phil Plait’s Bad Astronomy blog entry where I saw this.



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Playing soccer in a business suit with lions

Posted on by June 6, 2014
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Here’s something you don’t see every day: A man interested in the welfare of wild animals including lions who hangs out with wild lions in the bush and even naps with them. They seem to like him, possibly because he dresses well and plays soccer with them (thus one again demonstrating that everybody outside the U.S., even lions, is into soccer).


Link: http://youtu.be/JpyR-Ym7Hck

Actually, his wearing a suit probably has something to do with the fact that this video is sponsored by fashion firm Van Gils.

Update: That’s a really hard headline to write. “Playing soccer is a business suit with lions” sounds like the business suit has pictures of lions on it or something. “Playing soccer with lions in a business suit” is ambiguous as well. “Playing soccer with lions while wearing a business suit” is reasonably clear but wordy…



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John Oliver’s excellent piece on net neutrality

Posted on by June 3, 2014
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HBO’s John Oliver does an excellent job explaining why net neutrality is important and why politically powerful opponents are winning the game. (As he points out, it was Obama who nominated a top cable company lobbyist to head the FCC.)

Note, incidentally, that Oliver fearlessly attacks Time Warner in this clip despite the fact that Time Warner owns his network, HBO.


Link: http://youtu.be/fpbOEoRrHyU



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Republicans on global warming

Posted on by November 8, 2015
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Not many years ago most Republican leaders accepted the scientific consensus on human-caused global warming, as this video reminds us:


Link: http://youtu.be/ckxLgsUQmHg

It’s remarkable that the GOP has shifted so far so fast under pressure from the extremists who tend to have disproportionate influence on the party’s primaries. Now it’s routine for many Republican leaders, even some of the same ones in the video above, to argue that any uncertainty is grounds for doing nothing — I wouldn’t want to be their passenger it a fog — and even to claim that global warming is a hoax. Which, of course, it isn’t; it’s basic chemistry and physics.

Of course, a multitude of things influence climate, and climate has been changing since long before humans started burning fossil fuel. No one suggests otherwise. When people bring this up in the context of discussing modern global warming, it suggests a fundamental misunderstanding, an assumption that scientists are guessing when they attribute observed warming to carbon dioxide from burning fossil fuels. In fact, human-caused global warming was predicted in the 1800s before it was observed, based on the straightforward fact that carbon dioxide absorbs some wavelengths of infrared light and thereby traps heat that would otherwise radiate away into space. That’s a good thing; without greenhouse gases, the Earth would be mostly frozen over. But adding more carbon dioxide to the atmosphere necessarily means a higher temperature unless something else offsets it, and when we burn fossil fuels we’re putting carbon into the carbon cycle that has been locked away underground for tens of millions of years.

(Since fossil fuels also contains lots of hydrogen, burning them also releases water vapor, also a greenhouse gas, but there’s already so much water on the surface of the Earth the change is minimal.)

The subject came up in a Bell Telephone science special about weather broadcast in 1958 (see below). A mid-1960s National Academy of Sciences report requested by President Johnson had a section of the subject. I learned about it as a physics major in the early 1970s.

There was some discussion in the 1970s that particulate pollutants might increase the Earth’s albedo (reflectivity) enough to cool the planet, but it was soon clear that except during brief periods of major volcanic eruptions, particulates only moderately reduced the rate of global warming and did not cancel it.

Speaking of volcanoes, it’s sometime erroneously suggested that they release more carbon dioxide than the use of fossil fuels, but that’s not remotely true. In fact, we’ve been directly monitoring the increase in atmospheric CO2 for decades, and we also have a very good idea how much is being added by the burning of fossil fuel, and it’s clear that all of the observed increase in CO2 can be explained by human activity, which is enough to overwhelm the various natural mechanisms that remove carbon dioxide from the air.

Here’s a brief clip from that Bell Telephone special. It’s a bit alarmist in that today’s estimates are that it would take at least a century to produce the drastic rise in sea level described, but it certainly makes it clear that global warming was a return even in the 1950s.


Link: http://youtu.be/m-AXBbuDxRY

Update 2015 November 8: For a depressing example of how far some of today’s Republican candidates have regressed from the sensible positions presented in the video above, see this later post.



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There’s evidence that the smell of men soothes rats

Posted on by May 29, 2014
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This is just weird. Following is the summary of an article published in the May 2 issue of the journal Science:

Scientists have found that rodents feel 36% less pain when a male researcher is in the room versus a female researcher. The rodents are also less stressed-out. The effect appears to be due to scent molecules that male mammals (including humans, dogs, and cats) have been emitting for eons. The finding could help explain why some labs have trouble replicating the results of others, and it could cause a reevaluation of decades of animal experiments: everything from the effectiveness of experimental drugs to the ability of monkeys to do math. Male odor could even influence human clinical trials.



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