Answers to Five Interesting Questions

This is not a quiz; it's a few interesting questions with detailed answers. Enjoy.

1/5: What is the name of the most distant man-made object that has ever left our planet?

2/5: Why do we weigh a certain amount?

3/5: How big can black holes be?

4/5: How far into space have our first radio signals travelled?

5/5: What is the coldest temperature possible?

Detailed answers.

1/5

The space probe Voyager 1 left the Earth in 1977, two weeks after its twin, Voyager 2.
Voyager 1 continues to travel through space at over 61,000 kilometres per hour (38,000 miles per hour) and is the most distant man-made object that has ever left our planet.

To us, that speed seems very fast, but to put it into perspective:

Imagine if Voyager 1 were to change direction and travel towards Sagittarius A*, the black hole at the centre of our galaxy, the Milky Way. That epic journey would take roughly 450 million years.

As of June 2026, that small probe is over 25 billion kilometres (15.8 billion miles) from Earth.

Chances are that Voyager 1 will still be travelling through space when the last human on Earth dies.

I wonder if, in the distant future, another intelligent life form will discover our tiny probe.

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2/5

Weight is the result of the force of gravity acting upon an object, which can change if the force of gravity changes.

My mass on Earth is 80 kilograms (176 pounds), but if I took the next flight to the Moon and weighed myself there, it would display just over 13 kg (29 pounds), the reason being that the Moon's gravity is much less than that of the Earth; therefore, I am being pulled down on the scales with less force.

On Mars, my weight would be just over 30 kilograms (66 pounds). If it were possible to stand on the Sun (which I am not recommending), my weight would be over 2,230 kilograms (4,920 pounds). The Sun’s gravity is almost 28 times as strong as the Earth’s.

And if I were floating in outer space with no gravitational attraction from any objects, my weight would be very close to zero.

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3/5

TON 618 remains one of the largest known black holes in the visible universe, with estimates ranging from 40 to 66 billion solar masses, but astronomers have identified several other candidates with comparable or possibly greater masses (not confirmed).

These few lines should give you a better idea of how compact black holes are.

The Sun has a diameter of 1,392,680 kilometres (865,000 miles); to become a black hole, it would have to be compressed down to about 6 kilometres (3.7 miles) in diameter.

Our planet Earth is 12,742 kilometres (7,918 miles) wide. Hypothetically, all of its mass would need to be contained in a very dense sphere roughly the size of a grape before it became a black hole.

Yes, black holes are amazing objects.

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4/5

Regular radio broadcasting began around 1920. Radio waves travel at the speed of light, about 1.08 billion kilometres per hour (671 million miles per hour).

Signals transmitted in 1920 are now roughly 106 light-years from Earth, forming a sphere about 212 light-years in diameter centred on our planet.

If an advanced alien civilisation at the edge of that sphere immediately replied upon receiving our signal, a complete send-and-reply exchange would take about 212 years. Although that sounds enormous, our radio bubble is still tiny compared with the Milky Way, which is more than 100,000 light-years across.

The immense distances involved are one reason communication with extraterrestrial civilisations could be extremely difficult, if not impossible.

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5/5

The core of the Sun can reach temperatures of 15 million °C (27 million °F), but that is low compared to temperatures that occur in some other cosmic events.

The lowest officially recorded air temperature on Earth was −89.2 °C (−128.6 °F) at Vostok Station in Antarctica. The dwarf planet Pluto, whose average distance from the Sun is greater than that of any planet, has surface temperatures of about −233 °C (−387 °F).

Even colder is deep interstellar space, where temperatures are typically about −270.45°C (−454.81°F), only a few degrees above absolute zero, which is −273.15°C (−459.67°F).

Absolute zero, at −273.15 °C (−459.67 °F), is the lowest temperature theoretically possible.

British spelling throughout.

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