An object that does not give out light can be seen if it reflects light from another source. For example, we can see the Moon at night because it reflects sunlight. Other objects that can be seen by reflected light include planets, stars, and satellites.

Some objects can also be seen by their own thermal radiation. This is how we can see hot objects like the Sun, even though they do not emit visible light. Other objects that can be seen by their thermal radiation include stars, planets, and comets.

Finally, some objects can be seen by their magnetic fields. This is how we can see the Earth's magnetic field, even though it does not emit any light or thermal radiation.