Half the universe was missing... until now

What is the main reason scientists found it challenging to detect the Warm-Hot Intergalactic Medium (WHIM)?

• It is too far away from Earth.

• It only emits or absorbs specific types of high-energy ultraviolet or low-energy X-rays.

• It is hidden behind large galaxies.

• Its temperature is too low to be observed.

How can lightning from one side of Earth be detected on the opposite side?

• The sound waves travel through the Earth's core.

• The light from the lightning is reflected by the moon.

• Very low-frequency radio waves from lightning travel through the atmosphere and are guided by Earth's magnetic field.

• Satellites directly transmit the lightning flashes.

What causes the radio waves from lightning to create a "whistler" sound when detected on the other side of Earth?

• The radio waves bounce off the Earth's surface multiple times.

• The radio waves are slowed down by free electrons in Earth's magnetosphere, with lower frequencies slowing more than higher frequencies.

• The lightning strike itself produces a whistling noise.

• The radio waves interfere with signals from satellites.

How do Fast Radio Bursts (FRBs) help scientists find missing baryonic matter in the universe?

• FRBs are made of baryonic matter, so detecting them directly reveals its presence.

• The dispersion (spreading out) of FRB signals indicates the amount of ionized baryonic matter they passed through.

• FRBs create new baryonic matter as they travel.

• FRBs illuminate dark matter, making baryonic matter visible.