“Mistakes can be corrected by those who pay attention to facts but dogmatism will not be corrected by those who are wedded to a vision.” -Thomas Sowell
It’s hard to believe, but it’s already almost time for spring! After leaping an extra day to help keep our calendar in synch, March started off with an amazing string of stories over at Starts With A Bang, including:
- Why are maps of the cosmos oval-shaped? (for Ask Ethan),
- A new hope for our galaxy’s next supernova (for Mostly Mute Monday),
- Why college is so expensive, and how to fix it,
- The mystery of fast radio bursts deepens: they can repeat,
- The dark side of the Universe (a live-blog event of a fantastic Katie Freese talk),
- Hubble shatters the cosmic distance record, and
- Why does Earth appear blue from space?
For those of you hanging around the pacific northwest, I’ll be giving a public talk in Portland, OR on Tuesday, March 8th, and if you have questions you want me to ask to the Principal Investigator of LIGO, drop them off in the comments; I’ll be interviewing him on Tuesday! But for right now, let’s get into the bonus science of the week, and jump on into our Comments Of The Week!
From the incredulous Waterbergs on the proposed laser array to accelerate spacecrafts using a laser sail: “I think the maths has gone a little wrong here. You state that a laser in the gigawatt range would require an area of 100 square km. This implies a power of just 10 watts per square meter – massively below where we are at present – in fact by about a factor of a thousand at least. So actually the area required would be a rather small fraction of a square km, maybe just 100m by 100m – quite doable.”
Sure, if we use conventional, optical lasers that take advantage of terrestrial power sources you’re absolutely right. Is that what this project is proposing? You could read the white paper I linked to, and find the following relevant parts inside:
This approach also eliminates the conventional optics and replaces it with a phased array of small optics that are thin film optical elements. Both of these are a follow on DARPA programs and hence there is enormous leverage in this system. The laser array has been described in a series of papers we have published and is called DE-STAR (Directed Energy System for Targeting of Asteroids and ExploRation). Powered by the solar PV array the same size as the 2D modular array of modest and currently existing kilowatt class Yb fiber-fed lasers and phased-array optics it would be capable of delivering sufficient power to propel a small scale probe combined with a modest (meter class) laser sail to reach speeds that are relativistic. DE-STAR units are denoted by numbers referring to the log of the array size in meters (assumed square). Thus DE-STAR-1 is 10 m on a side, -2 is 100 m, etc. Photon recycling (multiple bounces) to increase the thrust is conceivable but it NOT assumed. The modular sub systems (baselined here at 1-4 m in diameter) fit into current launchers such as the upcoming SLS and while deployment of the full system is not our goal in the short term, smaller version could be launched to test proof of concept. As an example, on the eventual upper end, a full scale DE-STAR 4 (50-70 GW) will propel a wafer scale spacecraft with a 1 m laser sail to about 26% the speed of light in about 10 minutes (20 kg_0 accel), reach Mars (1 AU) in 30 minutes, pass Voyager I in less than 3 days, pass 1,000 AU in 12 days and reach Alpha Centauri in about 15 years.
So, sure, we could bring up our optimal laser technology and the power source for it, but that has the drawbacks of being heavy, expensive, and not rechargeable. Or we could set up a solar-powered, renewable system, which is still incredibly expensive but at least has a chance. Size isn’t the issue: cost and manageability is. That’s why the choices are the ones that have been made. It’s still not happening anytime soon, but it’s the best chance we’ve got with this new technology.
From SelfAwarePatterns on the two merging black holes from one star possibility: “Hmmm. I didn’t realize that GRBs that come from stellar collapses only come from a supernova (or hypernova) remnant collapsing into a black hole. I mistakenly assumed that any stellar collapse would generate the GRB. Interesting. Thanks. I stand corrected.”
It’s not that a GRB in general can’t come from something like two merging neutron stars; they can and are expected to, in fact. But the big issue is that if you want two black holes of ~30 solar masses each to come from a single star, you need a star whose destined-to-collapse core is at least that massive. And that means going over ~100 solar masses, easy, which really restricts what you can have.
But in general, I wanted to highlight this comment for something even more important; that last part:
I mistakenly assumed […] Thanks. I stand corrected.
A willingness to be wrong. A willingness to learn. A willingness to accept new evidence/information and grow. This is why — I like to think — we’re all here. So thank you for that moment of fulfillment, SelfAwarePatterns; I appreciate it greatly.
From Mark Slater on the Universe’s acceleration (kind of): “Before the big bang the whole universe was filled with hydrogen atoms. “
Oh my, no. This is a nice idea — the kind of idea you might have imagining what’s possible — but the kind that immediately falls apart when you try and confront it with testable propositions. Were these atoms neutral? If so, how did it survive the hot stage, and how do you account for the observations of Big Bang nucleosynthesis. If you want this to be a “well it was filled with hydrogen atoms, but then the Big Bang occurred,” then how do you explain all the successes and predictions of cosmic inflation, as well as the initial conditions of the Big Bang?
The difference between science and faith is that science is not only based on evidence, but that when we get new evidence or the evidence changes, our conclusions change, too. If you’re following a scientific process in your thinking, your conclusion — in your case, the thesis you started with — will change as you learn more.
From Denier on the future of star formation: “Every time a read an article like this that talks about peaks and decline, there is always a little part in the back of my brain that thinks for a moment ‘star formation peaked 10 billion years ago and we’re running out of the stuff to make new ones? WTF are we going to do?’”
If you want to do something about it, may I suggest “hydrogen collection.” You see, even though the star formation rate has been dropping (and will continue to drop) for billions of years, our Universe, by number of atoms, is still well over 85% hydrogen: somewhere around 88% or so. Considering it began as 92% hydrogen, very little has changed. (The change is more significant mass-wise; we’re down in the 60-somethings percent-wise.) The key, if you want to do something, is to figure out how to gather and burn this hydrogen to completion. Gravity will help, as this bok globule — currently just mostly molecular hydrogen — will someday collapse to form a low-mass, isolated star.
Right now, this contribution to the star-formation rate is negligible, but in perhaps quadrillions of years, it will be the dominant component. Star formation will not cease altogether in hundreds of trillions of years, but will continue at a slower pace. My estimates tell us that we have some ~10^18 years of lower rates of — but not a rate of zero — continued star formation, which means we have many millions of times the current age of our Universe where Milkdromeda will still have stars undergoing nuclear fusion. It’s not an answer to the “forever” problem, but pushing star formation out by another factor of 1,000 in time over what some naive extrapolators predict should help ease your mind a little.
From Sinisa Lazarek on projections: “Projections can really mess you sometimes. i.e. in Mercator projection (most widely used for earth).. Greenland as huge.. as big as Africa… when in reality it’s only about the size of Egypt.”
I like the Mercator projection of the CMB, above, to really emphasize how bad the area distortions are around the poles. The typical sizes of the red-and-blue spots at the equator and towards the poles are actually the same as one another, which gives you an idea of the catastrophe of this projection.
I’ll also share with you my favorite Mercator projection story of all. Typical maps of the world for many decades looked like this:
Where the defined “longitude = 0,” thanks to England, appears at the center. Note how a country like Russia appears discontinuous, as this is just the way longitudes line up on Earth. Other countries took to placing their country at the center of the longitude mark, but I was absolutely shocked when I took geophysics in college and had it taught by a French professor. His map of the Earth had France — most of France, I should say — all the way on the left-hand side, while the right side picked up again with the western tip of Africa and Iceland. In other words, the map was centered so that England was cut out of both sides, even at the expense of Spain, Portugal and a huge section of France itself.
To this day, that memory amuses me. Nationalist hatred leads to some bizarre things.
From Ragtag Media on the college tuition & hiring problem: “ETHAN YOUR SCARING ME!!!!!!! YOU Are Espousing “Conservative” Values?…:
“So what’s the solution? Join forces. Form a student-faculty union, and put pressure on the colleges themselves to move away from a model where the administration and the board of directors are the sole decision-makers here. Students and faculty have the most powerful weapons available at their disposal: to put their hands in their pockets and simply do nothing. If you want to change the system, you have to be willing to risk the security of the table scraps you’re receiving. Students: why should you pay so much for a bloated administration and for so little in terms of actual education? Faculty: why should you accept the ever-increasing work burdens for stagnant pay and colleagues who aren’t permanently employed? If we work together, we have everything to gain. We can fix the college/university system. We just need to be willing to work together to cut out the chaff while keeping the wheat.”
LOL… Good For You…”
I’ve always wondered why many people feel that if they’re conservative, then everything synonymous with good is also conservative, and everything synonymous with bad is liberal, while if they’re liberals, then everything synonymous with good is liberal, and everything synonymous with bad is conservative.
In this case, there are clearly elements of both political ideologies that I support here: unionization with the power to strike if necessary; smaller administration and the removal of unnecessary, bloated bureaucracy; empowerment of workers and service-purchasers; increased individual salaries/economic freedom and the removal of high-overhead services. You’re not the only one, Ragtag, to say this, by the way.
I’m actually proud of my Alma Mater, Northwestern, for coming up with a solution (albeit a different one) to make sure that people can afford it without coming out in crushing debt. Tuition there, by the way, at ~$48,000 per year, is approximately three times what it was when I went there, and I was there from 1996-2000. That’s a big increase in a short amount of time!
And finally from Dan Milton on why Earth appears blue: “Why do I get and endless loop of Forbes welcome pages?
Please make content accessible somehow.”
The Earth actually appeared blue until Forbes started distributing Malware and blocking ad-blockers. Now the Earth appears like this.
We had a good run, everyone. Thanks for stopping by, hope to see some of you in person on Tuesday, and have a great week going forward!