Sunday, March 15, 2009

What’s Wrong with "Parallel Universes" on the History Channel

While the TV series The Universe has much valuable content and I applaud every effort to make science more accessible, occasionally this program is incomprehensibly wrong. The episode Parallel Universes is heavy with hyperbole, and a grossly incorrect claim. It states as a matter of fact that scientists have shot lasers beams across the universe to measure its global flatness. That is total nonsense.

Reflecting laser beams off the other end of the universe and back to Earth is ridiculous in itself – we can’t even do that to all the planets within our own solar system. And even if that were possible, it would take at least 27 billion years for the laser beam to return at the speed of light. While that would allow plenty of time for commercials, we would all have turned off the show long before.

This completely erroneous statement was part of a description of the measurement of the curvature of the universe by NASA’s WMAP satellite that is a spectacular scientific achievement deserving better reporting. Max Tegmark of MIT explained that the curvature of the universe can be measured by measuring the angles of a triangle that has a vertex at the Earth and the other two vertices at a very great distance. He said if the sum of the triangle’s angles were 180 degrees then the universe’s curvature would be zero and its geometry would be called “flat.” If the universe were curved (in a fourth spatial dimension) like a balloon, then the sum of the angles would be more than 180 degrees. This episode didn’t mention this but the sum of the angles could also be less than 180 degrees, in which case the geometry of the universe would be hyperbolic, like a four-dimensional potato chip. All that is fine. Where they went wrong was when the narrator said “to find out, they shot laser beams into space and made a giant light triangle.” They then cut back to Tegmark who said “Now we can tell and the measurement is in and it works beautifully. The angles add up to exactly 180 degrees.” Let me emphasize that Professor Tegmark was not the one who said lasers were shot into space to make a giant triangle.

The Universe claims to have a scientific adviser for each episode. I find it hard to believe that any such advisor reviewed the final cut of this and numerous other episodes.

Wednesday, March 4, 2009

What might happen if the heavens align on December 21st 2012?

Why didn’t the world end when the heavens were even more perfectly aligned in 1997?

Because space is vast, and everything in the heavens is so very far away.

As I discuss in Everyone’s Guide to Atoms, Einstein, and the Universe, there are four forces in nature:strong, electromagnetic, weak and gravity. The strong and weak forces have very short ranges—no larger than the size of an atomic nucleus—less than a trillionth of an inch. The electromagnetic force between large objects is extremely small because their electric charge is extremely close to zero. That leaves gravity. Gravity is intrinsically the weakest of all forces—the gravitational attraction of an electron to a proton is less than a trillionth of a trillionth of a trillionth of their electrical attraction. But, unlike electromagnetism, gravity is attractive for all forms of matter—it relentlessly accumulates. The 10 (raised to the 57) particles in the Sun pull on every one of the 10 (raised to the 51) particles in the Earth, and all those infinitesimal forces, all 10 (raised to the 108) of them, add up to one huge force that holds Earth in orbit. This makes gravity the most powerful and most important force of all. On a cosmic scale, it is gravity that controls the fate of everything.

So how much influence does the force of gravity from celestial bodies have on us? Below is a table of the strength of gravity that various heavenly bodies exert on us stated in g’s, the acceleration of Earth’s gravity at its surface (g = 32 feet per second squared).

Heavenly --------- Its Maximum Gravity
Body ------------ at Earth's Surface in g's

Earth-------------------- 1

--------------------- 0.000,63
------------------- 0.000,003,8

----------------- 0.000,000,03
Other Planets
--------- 0.000,000,02

Milky Way
-------------- 0.000,000,000,02

Since Earth’s orbit is slightly elliptical, the Sun’s gravity here varies between 0.000,59 g and 0.000,63 g. Even though Jupiter is 26,000 times more massive than our Moon, it is always at least 1600 times farther away, making its gravity never more than 1% of the Moon’s. Worrying about how the motion of the planets affects us makes no sense at all. The gravity from our immense galaxy, the Milky Way is about 200,000 times less here than the gravity of the Moon. Even though we are drawn by 100 billion stars, they are so far away that their effect is immeasurably small. And, since our distance to the galactic center is quite constant, even its minute force doesn’t change regardless of the orientation of the Earth, Sun, etc. Worrying about where the Sun will rise relative to the galactic center also makes no sense.

On Earth, the gravity of all other celestial bodies is virtually negligible compared to the Sun’s—that’s why Earth orbits the Sun and not anything else. The Moon’s gravity is 100 times less important, and everything else is 100 times less than that. Even the Sun’s gravity is 1600 less here than Earth’s own gravity. From the North Pole to the equator, Earth’s gravity changes by 0.5%, 0.005 on the above table. Changing one’s latitude is 200 times more important than the varying distance to the Sun, 10,000 times more important than the position of the Moon, and a million times more important than the position of all the planets.

No worries Mate.