FTSE 100 shares: is the stock market bubble set to burst? Simply click below to discover how you can take advantage of this. Renowned stock-picker Mark Rogers and his analyst team at The Motley Fool UK have named 6 shares that they believe UK investors should consider buying NOW.So if you’re looking for more stock ideas to try and best position your portfolio today, then it might be a good day for you. Because we’re offering a full 33% off your first year of membership to our flagship share-tipping service, backed by our ‘no quibbles’ 30-day subscription fee refund guarantee. “This Stock Could Be Like Buying Amazon in 1997” Peter Stephens | Thursday, 7th January, 2021 Click here to claim your copy now — and we’ll tell you the name of this Top US Share… free of charge! See all posts by Peter Stephens Our 6 ‘Best Buys Now’ Shares I’m sure you’ll agree that’s quite the statement from Motley Fool Co-Founder Tom Gardner.But since our US analyst team first recommended shares in this unique tech stock back in 2016, the value has soared.What’s more, we firmly believe there’s still plenty of upside in its future. In fact, even throughout the current coronavirus crisis, its performance has been beating Wall St expectations.And right now, we’re giving you a chance to discover exactly what has got our analysts all fired up about this niche industry phenomenon, in our FREE special report, A Top US Share From The Motley Fool. Enter Your Email Address Image source: Getty Images. I would like to receive emails from you about product information and offers from The Fool and its business partners. Each of these emails will provide a link to unsubscribe from future emails. More information about how The Fool collects, stores, and handles personal data is available in its Privacy Statement. Fears of a stock market bubble that is set to burst are likely to have risen over recent months. The FTSE 100 has gained 35% since reaching its lowest point during the February/March 2020 bear market.However, it continues to trade around 13% down on the all-time high recorded in 2018. The short-term outlook for the world economy is challenging, of course. But there may be buying opportunities available for long-term investors at the present time.5G is here – and shares of this ‘sleeping giant’ could be a great way for you to potentially profit!According to one leading industry firm, the 5G boom could create a global industry worth US$12.3 TRILLION out of thin air…And if you click here we’ll show you something that could be key to unlocking 5G’s full potential…Stock market bubbles: part of FTSE 100 historyThe past performance of the FTSE 100 shows that stock market bubbles and subsequent crashes are part of its fabric. In other words, it has always experienced bull markets that are followed by bear markets, and vice versa. As such, the current bull market is very unlikely to last in perpetuity. This means that a bear market is almost inevitably set to take place at some point in future.Of course, predicting when that will happen is extremely challenging. Any number of risks could prompt a weakening of investor sentiment, as well as falling revenues and profitability for large-cap shares. At the moment, the outlook for the world economy is very uncertain. Coronavirus continues to negatively impact the performances of many businesses. And this could lead the FTSE 100 lower and cause the stock market bubble to burst. However, other factors such as low valuations within the index and a favourable monetary policy environment may yet push the stock market to record highs.Taking a long-term view of UK sharesThere are always difficulties in predicting when a stock market bubble will burst. So taking a long-term view of the FTSE 100 could be a sound move. This means ignoring potential short-term challenges that may cause high volatility over a period of months. Instead focusing on the valuations of companies based on their financial prospects over the coming years, is a better approach.Using this strategy, many large-cap shares appear to be cheap at the present time. As mentioned, the index itself is trading significantly below its record high, while a number of sectors — such as banking, travel and leisure and oil and gas — contain numerous companies with valuations that are substantially below their long-term averages.Certainly, buying FTSE 100 shares now may lead to paper losses in the near term should the stock market bubble burst. However, it appears as though the index’s price level may account for many of the risks faced by the world economy at the present time. Therefore, on a long-term view, large-cap shares could provide buying opportunities right now. Over time, the past performance of the index suggests that looking beyond short-term risks to focus on where shares will be priced in the coming years is a sound means of capitalising on market cycles.