Earth would be quickly sucked into the black hole, because the gravity around a black hole is much greater than the gravity around our Sun.

Earth would slowly spiral into the black hole, because the black hole is the same mass as the Sun so it would not spiral in immediately.

Earth’s orbit would not change, because the black hole is the same mass as the Sun.

The electromagnetic force follows an inverse cube law with distance, rather than an inverse square law.

Electromagnetic force only works on tiny particles, whose mass is very small.

Most objects are electrically neutral.

The electromagnetic force only works on scales of about the size of an atomic nucleus.

Electrical charge is cancelled out by mass.

5000 years

It depends on which direction they come from.

380,000 years

14 billion years

More than 3 K, because by the time the peak temperature is 10 mm, the Universe will be contracting.

More than 3 K, because higher temperatures correspond to longer wavelengths.

About 3 K, because temperature won’t change significantly with such a small change in wavelength.

Less than 3 K, because the Universe slowly cools down over time.

About 3 K, because wavelength is unrelated to the peak temperature.

Less than 3 K, because lower temperatures correspond to longer wavelengths.

The spectrum of 75 percent hydrogen and 25 percent helium is a perfect thermal radiation spectrum.

This radiation came from the temperature of the Universe.

The first stars that formed in the Universe must all have had the same temperature.

The spectrum of pure hydrogen is a perfect thermal radiation spectrum.

The dark matter in the Universe is a perfect thermal radiation spectrum."

The light from all the stars and gas in the sky averaged over the entire Universe is a perfect thermal radiation spectrum.

This radiation came from the heat of the Universe itself.

1 million years

10^10 seconds

3 minutes

10^-100 seconds

10^-10 seconds

300 years

300,000 years

hotter.

cooler.

larger.