The World

[asterroc]

I'm trying to understand something. Please answer the below questions to the best of your ability.

[Poll #1397877]

What I'm trying to understand is why my students are unable to distinguish between the planet Earth and the entire universe. For example, I said "1. How is the world (the planet Earth) going to end?
2. Which of the three scenarios for the end of the universe do YOU think is most likely?" And they answered #1 with "Big Crunch, Big Rip, or Heat Death," and for #2 picked their favorite. The correct response for #1 is "When the Sun runs out of Hydrogen in its core, it will expand as a red giant and engulf the planet Earth."

This time I explicitly wrote "(the planet Earth)" in the question to try and avoid the mix-up from the colloquial usage of the word "world". I think I need to just never ever use the word "world" again in astronomy.

Comments

[hitchhiker.livejournal.com]

The correct response for #1 is "When the Sun runs out of Hydrogen in its core, it will expand as a red giant and engulf the planet Earth.

okay, i got that one wrong :) was sure earth was too far away to be engulfed

[zandperl.livejournal.com]

Even if the Earth were not engulfed, I am pretty sure it would still be destroyed when those outer layers were shrugged off as the Sun becomes a planetary nebula. Certainly that would destroy the gas giants (since all they are is gas, and that's what the PN is as well, so they'd be blown away), but I'm not 100% sure the PN would destroy rocky or icy bodies.

[hitchhiker.livejournal.com]

i went googling and found this, which suggests that it will likely be vapourised

[zandperl.livejournal.com]

Interesting! It didn't occur to me that the Earth's orbit might not remain at 1AU. (Begging the question of whether we will redefine the AU always be the distance from the Earth to the Sun, or to always be 1.4960E11m.) The tidal bulge part either has a major error or else a severe oversimplification - things that spin FASTER have a tidal bulge, not things that spin SLOWER, so a larger Sun (which spins slower) should have less of a tidal bulge.