Posts tagged science

thisisaphysicsblog:

The Idea: The Big Bang was some sort of explosion that released matter or something, that apparently came from nowhere and happened at the beginning of time.

How it works: This is probably one of the most difficult-to-grasp subjects in physics, mostly because a fairly enormous background in mathematics and physics is required. Because of this, I will disregard that barrier to entry because I break the rules, damnit.

First, we need to shatter a big part of this idea: the Big Bang was not an explosion. The Big Bang itself was a rapid expansion of space itself. Think of it like this - it’s as if you were holding a ruler, measuring a pencil, when very quickly the ruler got really long. “Well, crap,” you might say, “how can I measure this pencil?” Fear not, young physicist, because the pencil expanded too. So did you. The separation between the fundamental particles of the universe increased. (I’ll get to the math reasons for this later.)

You may be thinking, ”But super-smart physics man, isn’t that just semantics? Does it matter if we call it an explosion or an expansion?” In fact, it does. An explosion implies that there was something to explode into! Currently, we don’t know anything about what our universe is “in”, what surrounds it. All we know for sure is the spacetime inside it, and it got bigger. It’s expanding right now! Galaxies move away from each other constantly, but we can observe them all moving away from us. Are we at the center of the universe? No, because we’re also getting further from all other galaxies! We can only move away because the thing we move in, space, is getting “longer”.

“Okay, smart guy,” you may think to yourself, “what about all that matter? The universe is huge and the stuff before the Big Bang is supposed to be small!” You would have a good point, except for a lot of not-so-good holes in your point! One thing to consider is the size of fundamental particles relative to the building blocks of the current universe, atoms. Atoms themselves are approximately 99.99999999% empty space, and that’s even considering the nucleons as three-dimensional objects (since leptons, such as electrons and muons, are usually considered points). Packing all the mass in the universe close together, at high enough temperature to make forces comparatively weak, is not unfathomable.

The math: The Friedmann-Lemaître-Robertson-Walker (known as FLRW or FRW) model of the universe has a very simple metric, given by the following relation (with units where the speed of light and Newton’s gravitational constant are equal to unity):

where dΣ is the spacial elements in any coordinate system. Generally, reduced-circumference polar coordinates or hyperspherical coordinates are used.

This is analogous to the Pythagorean theorem, as this simply measures the interval between two points. (I’ll explain why the time element is negative in a further post, but it is necessary to either have the time component or all of the space components negated.) The function a(t) is a time-dependent scale factor that changes the “spacing” of the spacial components of this interval. Depending on its derivatives, space can expand or contract. Current measurements have calculated the ratio of the time derivative of a(t) to a(t) itself to be approximately (72 km/s)/Mpc - strange units, to be sure, but it means that for every megaparsec the universe expands, its expansion speed increases by 72 km/s. This value is known as the Hubble parameter.

As long as the second time derivative of a(t) is positive, the universe is expanding. There’s many constraints on how this scale factor can evolve, depending on what energies dominate the universe - matter, radiation, and vacuum energy all have distinct relations to the density of the universe itself, with the vacuum energy solution remaining constant throughout all time and matter/radiation decreasing over time. This means, eventually, vacuum energy will dominate and the universe will expand forever.

So there you have it. The Big Bang was an expansion of spacetime itself, all the currently-existing matter (and energy!) was in that Big Bang, and the universe is expanding.

Maybe.

We’re pretty sure about this one. Next time we’ll explore something science is a little less sure about: magnetic charge.

(via pixyled)

abaldwin360:

When things get tough, lawmakers get creative. Faced with predictions that sea levels in the coastal areas of North Carolina will rise by a meter in the next century, legislators are considering bold action: making those predictions illegal. A bill being circulated in the Tarheel state would force scientists to estimate future sea levels on a linear path based on trends since 1900 — in other words, based on the simple assumption that trends always move in a straight line, no matter what.

Over in Scientific American, Scott Huler has some things to say about this:

Which, yes, is exactly like saying, do not predict tomorrow’s weather based on radar images of a hurricane swirling offshore, moving west towards us with 60-mph winds and ten inches of rain. Predict the weather based on the last two weeks of fair weather with gentle breezes towards the east. Don’t use radar and barometers; use the Farmer’s Almanac and what grandpa remembers.

Things like marriage rules involve changing social mores and those who feel that certain types of marriage are wrong can be understood and even forgiven. They’re certainly on the wrong side of history, but it’s a social issue where emotion understandably holds sway over things like evidence.

But while the rising sea may engender emotion, it exists in a world of fact, of measurable evidence and predictable results, where scientists using their best methods have agreed on a reasonable – and conservative – estimate of a meter or more of rising seas in the coming century. In 2007 the Intergovernmental Panel on Climate Change gave a hesitant estimate of up to 59 centimeters of rise -but even two years later that estimate already appeared low and scientists began to expect a rise of a meter or more.

No matter in North Carolina. We’ve got resorts to build and we don’t care what the rest of the ocean does – our sea isn’t going to rise by more than 15.6 inches. Because otherwise it’s against the law.

Huler’s amazing rant is well worth reading in its entirety. [Scientific American]

source

Outlawing accurate science and public interest in the name of money!

Good sweet baby jeebus.

My first thought on seeing this headline was “oh of fucking course, because we can’t have our million dollar beach homes and tourism trade disrupted.”

I feel like I have to take issue with even comparing this to marriage rights, though?  I mean it seems to me that the two are entirely unrelated.  Why does Amendment One even need to be brought into this discussion?

Granted, I can see both things as being incredibly embarrassing for NC on the whole, this is true.