Answer:
Large spherical regions from which no light is detected
Explanation:
A black hole is an object that has an extremely high density such that it possesses very powerful gravitational force that prevents the escape of all objects including light from it, and consumes nearby objects.
Due to the power of the gravitational force of a black hole, at the center, objects are infinitesimally compressed resulting in the inapplicability of the concept of space and time and the location is known as a singularity
Therefore, the search for black holes involves searching for <em>large spherical regions from which no light is detected</em>.
As long as the sound is inside the helmet of your space suit, it will travel
at the same speed as it would on Earth, through the same mixture of gases
at the same pressure. Once it passes through the visor of your space helmet,
its 'speed' has no meaning, since there's nothing for sound to travel through on
the moon, and it doesn't travel at all.
Answer:

Explanation:
We can use the equation for the speed

where x is the distance and t the time. In this case we know that the time spent was 2 hours and the distance was 150km. By replacing we have

I hope this useful for you
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