We are told by the 'scientific establishment', or the cult of all-things-science; that the planets must be billions of years old. This is because evolution needs as much time as possible, in order that the magic of gaseous vacuum to planets; life-from-non life; and microbe to mechanic occur. The holy trinity of evolution is mutations [which kills genomic material]; natural selection [which means nothing, you can only select what your DNA software code makes available]; and time. Take away time and the whole nonsense of evolution becomes untenable – even for the cult of science.

A good scientific article on the subject as to why the Sun might be younger than we are told is here. As the article asks:

“One recent source looking at variations in solar luminosity has it about 15% less at 2 Ga before present [2 billion years ago], about 20% at 3 Ga bp [3 billion years ago], and reaching a minimum of 26% less than today’s luminosity at around 4.2 Ga bp [4.2 billion years ago]. In 1972 Carl Sagan estimated the luminosity to be roughly 40% less than today at about 4.5 Ga bp [4.5 billion years ago]. Thus the questions come up, ‘How could life evolve?’ and ‘How did life survive?”

Secular scientists posit an old Sun, yet according to their own theories, the Sun 4.5 billion years ago, gave off less radiative energy than today. How then could life form on earth, when it would have been an ice-planet ? [link]

“An example of a heat problem for long-age thinking that affects Earth and the Sun is usually known as the faint young Sun paradox. Evolutionists believe the first living cell formed from chemicals on the early Earth about 3.8 billion years ago. At that time in the Sun’s life cycle it would have given off about 30% less light energy than today, and the Earth would have been much colder. Earth would likely have looked like a ball of ice instead of how it looks today. Thus life would not be likely to survive or evolve.”

And

The Sun. As the Sun ages, it increases in brightness and produces more heat. If the Sun is as old as claimed by mainstream scientists, 3.8 billion years ago the Earth would have had an average temperature of -3°C. [link]

Why would the Sun burn brighter now then in the past ?

“...the Sun derives energy by the thermonuclear conversion of hydrogen into helium, deep inside its core. There is convincing evidence that the Sun is getting at least half of its energy by this method. Such a thermonuclear source could power the Sun for nearly 10 billion years. Most scientists think that the Sun (along with the rest of the solar system) is about 4.6 billion years old, which means it would have exhausted approximately half its ‘life’.”

It is highly debatable that the Sun is as old as the mainstream 'consensus' states. If it is however, 5 billion or so years old, this would mean that it would have 'brightened' or produced more radiative energy by about 40% over that period of time, according to secular-scientific models. By implication this must mean that it will continue to burn brighter at a higher rate, and at some time, this increase in radiative energy will make life on Earth untenable.

There are however some obvious questions that can be asked - how and why would planets rotate for 5 billion years without the law of entropy taking effect including the Sun ? What was the impetus of the original 'spin' for all the planets [Buridan 1350]; and what now is the motive force of the rotation ? Why is Venus red hot [is it new?], and why does it rotate 'backwards' ? How do planets orbit for billions of years without 'moving' or being involved in a catastrophic cosmic accident thereby eliminating all life on Earth?

What if the mainstream view is utterly wrong ?

Velikovsky who was slandered and pilloried by the scientific establishment wrote about a young solar system [see here and here] and provides a lot of evidence that for example, Venus is a young planet, which is why it is red hot [1000 F on the surface]. It has not yet cooled. Before the 1960s the 'consensus' was that Venus was similar to the Earth in its atmospheric and surface 'evolution' and might even support life. Whoops. If Venus is young why not the Sun ? Perhaps Venus is not 3 or 4 billion years old but much younger ? [Velikovsky believed it is 3000 years old based on cultural myths, texts, the Old Testament etc though plenty of objections exist to this idea]. 

In the same vein most cultures have stories of not only Venus 'attacking' the Earth but also Mars [cosmic collision ?]. In this light the Earth's orbit would have changed and most likely life must have been wiped out. In this theory Mars collided or 'fought' with Venus, a depiction clearly presented in the Iliad and in every culture's memory. The ancients maintain that the two planets 'fought', became entangled, with Mars at 1/8 the size, being 'thrown' towards the earth. It must have appeared that the Gods were exacting revenge for human arrogance, pride, sin and deceit.

But any collision or even a near miss would imply a massive redirection of the Earth's orbit to the order of millions of km; and upset its relationship with the moon, which is vital for life, would it not? Life would likely be eradicated as the orbit of the Earth and its vital satellite the moon became deranged. There is not much evidence to go on:

“Venus’s orbit presently has an eccentricity of 0.007, almost a perfect circle. The moon is also nearly circular in its orbit, with an eccentricity of only 0.055. Such a low eccentricity for Venus does not seem to suggest a significant catastrophic event in the past. However, note that the orbital eccentricity is not a constant. For our moon, it is possible past impacts could have caused oscillations in the orbit, though it is not clear if there is observational evidence of this.” [link]

On the other hand the ancient Greeks [Plato etc.] wrote that the Sun rose in the West....were they mad or just reporting what they saw or remembered; namely a catastrophic magnetic reversal of the poles and the earth's rotation due to some variety of cosmic upset ?

Science is the never-ending pursuit of what is true. In this light it appears that the more we study the cosmos the less we really know. We should not blindly accept therefore, that the Sun is 5 billion years old. We don't know how old it really is.