THE SOUTHWORTH PLANETARIUM
207-780-4249 www.usm.maine.edu/planet
70 Falmouth Street Portland, Maine 04103
43.6667° N, 70.2667° W
Founded January 1970
"Whatever you can do, or dream you can, begin it. Boldness has genius, power, and magic in it." -W.H. Murray (1913-1999)
THE DAILY ASTRONOMER
Tuesday, April 26, 2016
Darker Pandora
Last
week during our Pandora fest, we found to our horror that we had
neglected two questions tucked deep within the dark depths of Pandora's
jar. Ironically, both of them pertain to darkness, at least in some
respect. To those subscribers who posted these queries and then
thought we were neglecting them, we offer our sincerest apologies.
"What would we on Earth experience if the sun were to 'shut off' instantaneously? i know this is a scary concept, but i find it
fascinating."
-Annie A, Asheville, NC
Agreed. That concept is rather scary. Just to allay anybody's concerns, we are confident that the Sun will remain active and highly energetic for billions of years to come. However. we'll pretend that the Sun suddenly "shuts off" for whatever reason. What would we experience?
Well, for the first 8.3 minutes or so, we wouldn't experience much of a change because the Sun is about 8.3 light minutes away. About 8.3 minutes after the snap off, the Sun would appear to vanish. We would have instantaneous night fall on every part of Earth. No twilight would precede the darkness because twilight is caused by atmospheric light refraction of the Sun when it is below, but within 18 degrees of, the horizon. In this scenario, the light source, itself, vanishes.
We would not die at once. After all, we don't all die after each sunset.
Our
planet would rapidly cool as its main energy source would no longer be
imparting heat and light onto it. The lakes and ponds would solidify
and the air would become much colder. (Curiously. geothermal heat
would still provide some heat to the oceans, which, according to one
estimate, would require one million years to freeze solid!)
Humans
all over the globe would frantically try to remain warm with
conventional heat sources. However, the real problem would involve the
ecosystem. The photosynthetic process would be curtailed by the lack
of solar energy. Plant life all over the globe would perish,
disrupting the symbiotic oxygen-carbon dioxide exchange that sustains
life on this planet. Moreover, the atmosphere, itself, would
eventually freeze out of the sky and settle on the ground. However, by
that time, we would have all died by hypothermia or slow suffocation.
As for Earth, itself:
If
the Sun remains in place, but just goes dark, Earth and the other
planets will continue to revolve around it. The remains of the Sun
would appear as just a dark circle migrating across the sky. We would
only "see" that circle by observing the half-degree patch that was devoid of stars.
If
the Sun, itself, vanishes, then Earth and the other planets will start
traveling along a path tangential to their orbits. All the planets
will hurl through interstellar space like the renegade worlds we
discussed yesterday. The constellation shapes won't appear to change
much even over thousands of years. Only after great periods of times
would even these pattern become distorted, a combined effect of the
stars' proper motions and Earth's changing position in the galaxy.
"How do we know dark matter exists if we can't see it?"
-Bruce M, Cumberland, ME
Here, we harken back to an astronomical adage "If it isn't observed, it is inferred."
Dark matter refers to material that doesn't emit electromagnetic radiation. Astronomers study celestial objects by studying the EM radiation they exude into the Universe. They detect dark matter by observing how it affects visible matter in its vicinity. For instance. astronomers can measure the speeds of stars as they describe orbits through galaxies. The amount of matter within a galaxy determines the stellar velocities. The greater the galaxy's mass, the faster the stellar motions.*
